Lifting-jack



J. C. KOPF.

LIFTING JACK,

APPLICATION FILED FEB. 4*. I92].

Patented Nov. 22, 1921.

2 SHEETS SHEE? J. C. KOPF.

LlFTlNG JACK.

APPLlCATiON FILED $158.4. 1921'.

1,397,870. Patented 'Nov. 22, 1921.

ZSHEETS-SHEET 2.

shoe/whoa UNITED STATES PATENT OFFICE.

JOHN C. KOPF, OF BELLEVUE BOROUGH, PENNSYLVANIA, ASSIGNOR To THE DUFF MANUFACTURING COMPANY, OF PITTSBURGH, PENNSYLVANIA, A CORPORAT OF PENNSYLVANIA.

LIFTING-JACK.

Application filed February 4, 1921.

T 0 all whom it may concern:

Be it known that I, J on): C. Korr, a citizen of the United States, and a resident of the borough of Bellevue, in the county of Allegheny and State of Pennsylvania, have invented a new and useful Lifting-Jack, of which the following is a specification.

This invention relates to lifting jacks of the kind that is operated through a worm and worm-wheel rotating a pinion meshing with rack-teeth on the lifting-bar, the worm and worm-wheel being of steep-pitch so as to reduce the end-thrust resistance to manual operation, and consequently requiring to be held in order to sustain the load; the holding means being ordinarily a constantly applied brake. In a prior application, Senal No. 405,401, filed August 23, 1920, I have disclosed an improved jack of this type, having in its combination a holding device which utilizes this end-thrust of the lifting worm, and which is therefore, necessarily reliable and also permits of easier operation since its resistance to lifting and lowering by the operator is only what the load requires to sustain it. According to the present invention a jack thus constructed which is lifted manually by power applied to the worm-shaft overcoming the friction of the holding device, is lowered automatically by controllably relieving the thrust pressure, and thereby the friction, in the device, so that the loaded rack-bar comes down by itself.

In the accompanying drawings, forming a part hereof:

Figure 1 is an elevation of the jack, looking at the interior with the cover-plate removed;

Fig. 2 is a sectional elevation looking at right angles to Fig. l; and

Fig. 3 is a horizontal section in the plane of the section of the operating shaft, which, with the lowering device is seen in plan elevation.

The jack has a stand frame 1, in which a jack-bar or acking member 2, provided with rack teeth 3 on one side, is vertically guided.

The rack teeth are meshed by a pinion 4: cut on a shaft 5, which is journaled in front and rear bearings 6 and 7 in a gear case 8, the bearing 6 being removable to permit the insertion of the pinion into its rear Specification of Letters Patent.

Patented Nov. 22, 1921. Serial No. 442,368.

10 of the gear case, rendered accessible by a cover 11, 1s a worm-wheel 12, larger than the pinion.

An operating shaft 13 is arranged transversely below the axis of the pinion and worm, in bearings half in the body of the frame and half in the cover 11; and on this shaft within the chamber 10 is a worm 14 meshing the worm-wheel. A lever rocker or ratchet case 15, socketed for the reception of a handle-bar and containing a double reversible pawl 29, is mounted to oscillate on the outwardly projecting portion of this shaft, in cooperation with a ratchet wheel 16 fixed on a hexagonal seat 17. By means of this ratchet lever the load is lifted.

When load is on the rack-bar, whether at rest, or when lifting or lowering, the action of the load is transmitted and reduced through the gearing and applied to the worm, where because of the pitch its effect is partly to rotate the worm 14 and partly to press it endwise, creating a constant moderate end-thrust pressure, toward the right in Fig. 1. Between this end of the worm and the frame there are introduced, in accordance with my prior invention two disks 18 and 19 having fiat smooth surfaces to cooperate with each other and with similar surfaces 20 and 21 formed on the end of the worm and the interior of the frame. The disk 18 has a round central opening encircling the shaft, and an external notch 23 which engages an anchoring rib 25 projecting from the rear wall of the chamber 10 of the frame. This disk is thus held against rotation, while free to be pressed axially against the disk 19. The latter disk is engaged to rotate with the shaft, while also free axially, by means of lateral notches 25 in its interior opening and a cross-pin 27 in the shaft, the ends of which project into the notches. There are thus three friction surfaces which are rotatable with the shaft and worm, and three opposed surfaces which are stationary in respect to rotation, the alternating fixed and rotatable elements being adapted to be compacted by the end-thrust against the abutment support of the frame. Through the friction thus produced, the load is securely held by its own action against running down, the holding being proportional to the load; so that the lighter the load the less the resistance. Therefore, the friction, while always sufficient to hold the load, is easily overcome bythe handle leverage upon the operating shaft in lifting and lowering.

Additional pressure of small amount is provided by a light spring 28 encircling the shaft between the other end of the worm and the remote wall of the chamber. This spring serves to prevent the ratchetvwheel 16 being dragged back by the spring-pressed pawl 29 on the upstrokes of the lever, when the ackend of the shaft remote from the ratchet lever. This screw is provided with a handwheel 33,,by means. of which the screw can be readily and exactly moved in and out. The end of the shaft is caused to project into the back or inner end of this socket, so that when the'screw is advanced slightly it pushes back on the shaft against the end-thrust pressure derived from the load. This relieves the pressure, andv consequently the friction, between the surfaces of the holding device, and thereby permits the shaft to rotate under the action of the load, which sinks with the rack-bar. ,As the friction surfaces are flat and smooth and the slight end movement is delicately adjustable by the screw, the descent can be very nicely controlled. When lowering in this manner, the handle-bar is'of course removed from the socket 15, and the latter may revolve with the load,,a friction-holding device actuated by the end-thrust of the worm, and means for relieving the end-thrust pressure in said holding device to let the rack-bar run down by gravity.

2. In a jack, the combination with a frame, a rack-bar, a pinion meshing with the rack bar, a worm-wheel on the axis of the pinion, an operating shaft, and a worm onthe op erating shaft meshing the worm-wheel, said worm andworm-wheel of steep pitch, of a ratchet-lever lifting device on one end of said shaft, friction-holding disks interposed between the worm and the frame, and a lowering device adapted to act upon the end of the shaft remote from the ratchet-lever device in opposition to the end-thrust-on said disks.

.JOHN C. KOPF. 

